Conventionally, domestic laundry washing and drying machines have been separate units. The user first places laundry in a washing machine, in which the laundry is washed, rinsed and then spun to remove most of the water. Once it has been washed etc., the wet laundry is then transferred to a laundry drying machine. This is inconvenient in many respects. Firstly, two separate machines have to be provided, both of which are relatively bulky. The cost of two machines is quite high and one can note that many of the basic control elements, e.g. the cabinet, motor, clutches, tub and control electronics are duplicated. While having two machines can theoretically enable a higher throughput, as both machines can be run simultaneously, this is difficult to achieve in practice and requires close monitoring of the machines to ensure prompt removal of the laundry or transfer, when each machine finishes its cycle. Practically, for most domestic use, the throughput available with a single combined machine would be sufficient.
A review of the prior art shows that numerous attempts have been made in the past to provide a combined washer and dryer, but to applicant's knowledge all of these have been unsuccessful. While some designer's have appreciated that it is desirable to provide a tub or basket having an axis which can be tilted between a vertical position for washing and a horizontal position for drying, they have generally failed to recognize that the requirements for this drum or basket are quite different for the two actions of washing and drying. Thus, in conventional, separate washing and drying machines, the basket for washing is of relatively small diameter and includes a central agitator that oscillates about a vertical axis, to wash the laundry in the machine. For drying, a drum having a relatively large diameter rotates about a horizontal axis, to create a tumbling action to promote a flow of heated air through the laundry, to dry the laundry. A drum for drying typically is totally unobstructed in the middle and includes a small number of baffles around the periphery to engage the laundry and cause the tumbling action. Thus, a tub configured for providing a washing action is not suitable, even if mounted for rotation about a horizontal axis for drying the laundry. Similarly, a tub or drum configured for a drying action, is wholly unsuited for providing the agitation for washing laundry, whatever the orientation of the drum.
In the foreign patent literature the following references, all dating from approximately the same period, show early examples of attempts at providing a dual function machine: German Patent Specification 853,434; French Patent 1,016,540; and British Published Specification 913,485.
The French and German proposals both appear to teach a proposal in which a drum or the like can be tilted between two different positions, with its axis either horizontal or vertical to provide the two different functions of washing and drying. A different approach is taken in the British specification, which provides a cylinder for washing, and proposes moving the cylinder with the laundry in it from the washing machine to an extraction machine, without the provision of any drying step.
An early proposal in the U.S. art is U.S. Pat. No. 2,782,622. Here, the drum is only tilted through a small angle, and again a single drum of fixed configuration is intended to provide both the washing and drying actions.
A so-called washing, dehydrating and drying machine is disclosed in U.S. Pat. No. 5,058,401. The apparatus here is extremely complicated, and somewhat unusually, provides a spherical container for the laundry, comprising two hemispherical members molded from resin. The patent teaches three separate steps, namely: washing with rotation about a horizontal axis; spinning about a vertical axis; and drying by rotation about the horizontal axis. U.S. Pat. No. 5,074,131 describes a combined washer and dryer that rotates a tub to approximately 75% for the vertical to initiate the drying mode. This invention utilizes a so-called pulsator to wash the laundry. A somewhat similar proposal can be found in U.S. Pat. No. 5,111,673 which also utilizes a pulsator. In both of these proposals, the pulsator could be characterized as truncated agitators from conventional washing machines which are intended to provide sufficient agitation, while leaving the drum or basket largely unobstructed, so that a tumbling action for drying can be provided. It is believed that such a compromise will impair both the washing and drying actions. Thus, the agitator will probably be insufficient to provide a good washing action, while at the same time it will still be present to interfere with the tumbling action for drying.
Accordingly, what the present inventor has realized is that, in order to provide a combined washing and drying machine, it is necessary to provide some mechanism within the tub or basket, which will enable an efficient washing action to be provided, while at the same time leaving the basket unobstructed for tumbling action during drying. The introduction of a perforated washing plate meets these requirements. By forcing water through the laundry the plate provides a more effective cleaning action than the agitators or pulsators in the prior art. Moreover, the present inventor has realized that it is also desirable to be able to adjust the effective size of the basket, to accommodate different size loads. This becomes particularly important where the basket is large enough, i.e. has a relatively large diameter in volume, so as to be suitable for drying.